The NSF AMISR Project:
New Eyes on Magnetoshere-Ionosphere Coupling
Joshua Semeter
Boston University Center for Space Physics
Monday, December 20, 2010
1
Tutorial Outline
1. How does ISR work?
2. Electronically steerable ISR: A new radar modality for space science
3. Selected Science Highlights: Harang reversal and substorm
dynamics
4. Concluding Remarks
Monday, December 20, 2010
2
Poker Flat Incoherent Scatter Radar
(PFISR)
Poker Flat, Alaska
EISCAT
ESR
PFISR
Resolute Bay
Sondrestrom
Millstone Hill
Jicamarca
Monday, December 20, 2010
Arecibo
3
How does a Doppler radar work?
Two key concepts:
Distant
Time
R = cΔt 2
Velocity
e-
Frequency
v = − f D λ0 2
A Doppler radar measures backscattered power as a function range and velocity.
Velocity is manifested as a Doppler frequency shift in the received signal.
Monday, December 20, 2010
4
How does a Doppler radar work?
Two key concepts:
Distant
Time
R = cΔt 2
Velocity
Frequency
v = − f D λ0 2
A Doppler radar measures backscattered power as a function range and velocity.
Velocity is manifested as a Doppler frequency shift in the received signal.
Monday, December 20, 2010
5
J. Semeter, Boston Un
her
Doppler
Spectra
How
does a Doppler
radar work?
Two key concepts:
Distant
Velocity
Frequency
v = − f D λ0 2
J. Semeter
Power (dB)
Time
R =Remote
cΔt 2 Sensing
ENG SC700 Radar
Some Other Doppler Spectra
NEXRAD WSR-88D
gine
at give Doppler spectrum
Velocity (m/s)
S. Bachma
If there is a distribution of targets moving at different velocities (e.g., electrons in the
ionosphere) then there is no single Doppler shift but, rather, a Doppler spectrum.
What is the Doppler spectrum of the ionosphere at UHF ( λ of 10 to 30 cm)?
Tennis ball, birds, aircraft engine
Monday, December 20, 2010
6
de, which is the main mode detected by ISRs, and the Langmuir
Longitudinal modes in thermal plasma
on, 2003]. Using a linear approach to solve the Vlasov-Poisson
DIAZ ET AL.: BEAM-PLASMA INSTABILITY EFFECTS ON IS SPECTRA
X-6
DIAZ ET AL.: BEAM-PLASMA INSTABILITY EFFECTS ON IS SPECTRA
dispersion relation of these modes is obtained. The real part of
�
��
� � � �1 � �3
DIAZ ET AL.: BEAM-PLASMA
EFFECTS
π
me 2 INSTABILITY
Te 2
Te ON�3IS SPECTRA
�
��
3(2)
+
exp − � − � ωs � 1
n relationωreads
�
�
si = −
27 Te
8
mi
Ti
2Ti π 2 me 2
Te 2
3
ωsi�= −
+
exp −
−
ωs
�
��
�
Ion-acoustic
�
� � 12 � � 32
8 dependence
mi
Ti mode
2Ti 2
Cs = kB (Te + 3Ti )/m
ion-acoustic
speed.
The
of
this
π i ismthe
T
T
3
e
e
e
ωsi = −
+
exp −
−
ωs
(2)
�
-6
DIAZ ET 8AL.: BEAM-PLASMA
INSTABILITY
EFFECTS
ON
IS
SPECTRA
mi Cs =Ti kB (Te + 3T
2Ti )/m
2 is the ion-acoustic speed. The dependence of
i
where
i
ω
=
C
k,
(1)is detected by
spheric state parameters
s
s is observed in Eq. 2. The Langmuir mode
�
= kB (Te + 3Ti )/mi is the
ion-acoustic speed. The
dependence
of this mode
�
�
��
on ionospheric
state
parameters
is observed
in Eq.
�
1
3
� its �dispersion
der certain conditions, and
the�real �
part
of
relation
is expressed
as 2. The Langmuir mode is d
2
2
assuming ωsi � ωs , k 2 λ2De
�
1
and
T
/T
�
1)
can
be
written
i Tee
π
me
Te
3
ωsi = − is observed in +Eq. 2. The
expLangmuir
−
−
(2)
pheric state parameters
mode isωsdetected by
� 8
mi certainTconditions,
2Ti the2 real part of its dispersion relation is exp
i 3
ISR
under
and
2
2
2
2
(3)
� ωL = ωpe + 3 k vthe ≈ ωpe + 2 vthe λDe k ,
er certain
conditions,
and
thei real
part
of its dispersion
relation
is expressed
as mode
here
C
=
k
(T
+
3T
)/m
is
the
ion-acoustic
speed.
The
dependence
of
this
s
B
e
i
�
Langmuir
3
2
ω
=
+
≈
ω
+
v
λ
k
�
L
pe
the De ,
e imaginary part (assuming ωLi � ωL ) is
3
2 by
ionospheric state parameters
is observed in Eq. 2. The Langmuir mode is detected
ω = ω2 + 3 k2 v2 ≈ ω + v λ k2,
(3)
2
ωpe
L
pe
the
pe
3 k2
2
vthe
the De
2
R under certain conditions,
and imaginary
the real
of its
dispersion
relation
� part
�
73 �
and 3the
part
(assuming
ωLi
� ωL )isisexpressed as
2
ω
ωpe
π6:36am
1 ω ) is
3 D R A F T
Maypart
29,
2010,
pe �
maginary
(assuming
ω
Li
L
ωLi ≈ −
exp
−
−
ωL .
(4)
3
2
�
3
2
8 k vthe
2k vthe 23
2
2
2
ωL = ωpe + 3 k vthe ≈ ωpe + vthe λDe k 2 ,
(3) �
�
�
3
2
� parameters2�
orward model used to �
estimate ionospheric
in ISR
assumes
that
these
ω
ω
π
1
3
pe
pe
3
2
Figure
2·4:
Longitudinal
modes
of
a
ωpeωLi ≈3 −
exp − 2 2 − plasma.
ωL . Blue lines re
π ωpe 1
3
3
ωLi part
≈ − (assuming
exp − L ) is
− acoustic
ωL .8 waves
(4)Langmuir
kbeam
vthe
vthe 2waves.
and
red
ones 2k
to
ddominating
the imaginary
3 ωLi � ωHowever,
2
3
2
modes
in the8 ISR
spectrum.
an
injected
of
particles,
k vthe
2k vthe 2
The forward
model
usedthe
toinestimate
ionospheric
parameters in ISR assumes
icular
canto74destabilize
the plasma,
altering
dispersion
relations
and
rward electrons,
model used
estimate
ionospheric
parameters
ISR
assumes
that
these
start to interact more strongly with the growing wav
� plasma particles �
�
3
2
ωpe
π ωpe
1
3
This
can
sometimes
terms of
Monday, December 20, 2010
75
are
the
dominating
modes
in
the
spectrum.
However,
an so-called
injectedquasi-linea
beam 7of
exp −
− ISR
ω be
. described in
(4)the
udes of these modes. ω ≈ −
otion
has The
to be name
used. The
system of equations
formed
fieldequation,
equations.
“Particle-in-Cell”
comes
from the way of
um at high latitudes, therefore a kinetic approach, which
ch
includes
the simulation
Vlasov equation
plus Maxwell’s equations, has
ntities
to
the
particles.
n equation, has to be used. The system of equations formed
y to obtain the wave modes propagating along the plasma.
odes
solve
equation
of motion
of particles
withhas
the Newton-Lorentz
includes
thethe
Vlasov
equation
plus Maxwell’s
equations,
Plasma simulation
ρ=
= 0ρ(x1 , v1 , . . . , xN , vN ),
∇
·
B
ge and current densities.
Frequency (kHz)
obtain the wave modes propagating along the plasma.
∂fj (t, x, v)
qj
∂fj (t, x, v)
·
+
(E + v × B) ·
=0
(2.3)
∂x
mj
∂v
(PIC):
fj (t, x,Particle-in-cell
v)
qj
∂fj (t, x, v)
+
(E + v × B) ·
=0
(2.3)
∂x d v
mqj
∂v
i
i
−∂B) + v × B(x ))
20
d
=
(E(x
for
i = (2.4)
1, . . . , N
(2.49)
i
i
i
∇
×
E
=
dt
mi
∂t
−∂B
20
∇×E=
(2.4)
96 of
∂t
quations (Equations
2.4 and 2.7) together with the prescribed rule
ρ
1 ∂E
∇
·
E
=
(2.6)
∇ × B = µ0 J + 2
(2.5)
�0
c ∂t
J
ρ 1 ∂E
∇
·
E
=
(2.6)
∇ × B = µ0 �J + 2
(2.5)
3000
0
c ∂t
Langmuir (“Plasma Line”)
∇·B=0
(2.7)
(2.50)
Ion-acoustic (“Ion Line”)
(2.51)
0
(2.7)
J = densities.
J(x1 , v1 , . . . , xN , vN ).
ge andSimple
current
rules yield
�
� �
qj ncomplex
qj behavior
fj d3 v
(2.8)
j =
�
jcharge and
j current
�
�
density
of the medium at certain iteration. A
3
q j nj =
qj
fj d v
(2.8)
�
j
j
PIC simulation
is given in Figure 2·8.
�the
�
-3000
qj nj vj =
qj
fj v d3 v,
(2.9)
20
40
60
80
100
�
j
ly are classified
depending on dimensionality of the code andkon
�
�
= 2the
π λ (1/m)
3
qj nj vj =
qj
fj v d v,
(2.9)
(a)
ce-velocity distribution
function of the species j, �0 and
j
ations
used.20,The
Monday, December
2010 codes solving a whole set of Maxwell’s equations are
120
8
ISR measures a cut through this
surface at a particular wave number
77
31
96
Frequency (kHz)
3000
150
Langmuir (“Plasma Line”)
0
-3000
Ion-acoustic (“Ion Line”)
20
40
60
k = 2π λ
(a)
-150
20
40
60
k = 2π
80
100
λ (1/m)
120
Sondrestrom
EISCAT UHF
Monday, December 20, 2010
120
AMISR, MHO
Ion-acoustic “lines”
are broadened by
Landau damping
80
100
(1/m)
0
9
Incoherent averaging
Normalized ISR spectrum for different integration times at 1290 MHz
1 sample
30 samples
We are seeking to estimate the
power spectrum of a Gaussian
random process. This requires
that we sample and average many
independent “realizations” of the
process.
1
Uncertainties ∝
Number of Samples
600 samples
Monday, December 20, 2010
10
Exact expression for the radar cross
section of the ionosphere at UHF
where:
From Evans, IEEE Transactions, 1969
Monday, December 20, 2010
11
Standard parameters found by fitting
the Ion-acoustic line
Te/Ti
Ti/mi
Vi
area ~ Ne
Ion temperature (Ti) to ion
mass (mi) ratio from the
width of the spectra
Electron to ion
temperature ratio (Te/Ti)
from “peak-to-valley” ratio
Electron (= ion) density
from total area (corrected
for temperatures)
Line-of-sight ion
velocity (Vi) from bulk
Doppler shift
Monday, December 20, 2010
12
Altitude dependence
Monday, December 20, 2010
13
Conceptual Framework for MIC
research with ISR
Magnetospheric
Process
Inference
Modification of the
Ionospheric State
(density, temperature, flow)
Inversion
Changes to Intrinsic
Plasma Wave Spectrum
Estimation
Complex Voltage
Received at the
Radar
Monday, December 20, 2010
14
Dish Versus Phased-array
-FOV: Entire sky
-Integration at each position before
moving
-Power concentrated at Klystron
-Significant mechanical complexity
Monday, December 20, 2010
-FOV: +/- 15 degrees from boresight
-Integration over all positions
simultaneously
-Power distributed
-No moving parts
15
Selected AMISR highlights
✤
Harang reversal and substorm onset
✤
2D imaging of ionospheric flow fields and their relation to auroras
✤
3D imaging of ionospheric state during a substorm
✤
Ion acoustic turbulence
Monday, December 20, 2010
16
The Harang Reversal Region and
Substorm Onset
J//
E
Cross tail current
Finite width of tail
Less energetic
protons from LLBL
Median energy
proton drift pass
More energetic
protons from far tail
The Harang reversal results from dawn-dusk pressure asymmetry in the
near-earth plasma sheet [Erickson et al., 1991, JGR]
courtesy Shasha Zou
Monday, December 20, 2010
17
The Harang Reversal Region and
Substorm Onset
Ionospheric Equipotentials
Bz< -7.25 nT
By=0
Harang
reversal
Electric field
E x B drift
18
Discovered by Harang [1946]
 Characteristics:
Electric fields reverse
Flow shear
Eastward and westward electrojets overlap

Based on Weimer, [1995]
courtesy Shasha Zou
Monday, December 20, 2010
18
Magnetic
Distance
MagneticNorth
North Distance
(km)
2D Imaging of Convective Flows
400
350
300
250
200
150
100
50
!150
!100
!50
0
50
100
Magnetic East Distance (km)
150
Magnetic East Distance
Semeter et al., JGRA 2010
Monday, December 20, 2010
19
Spatiotemporal characterization of
substorm dynamics
Onset Overhead
Onset to the East
20
from Zou et al., JGRA 2009a, 2009b
Monday, December 20, 2010
20
Direction
Thin breakup arc
occurs in the center
of HR, which forms
during growth
phase;
Magnitude
Flow vectors
Protons
E-region
ionization
after onset
Electron Density
H perturbations
reverse sign,
indicating magnetic
Harang Reversal.
Ground
Magnetometers
21
Monday, December 20, 2010
21
Assimilative model of substorm
sequence
X
Jp
X
X
Jp
X
See Zou et al., JGRA 2009a, 2009b; Lyons et al., JGRA 2009; Lyons et al., JASTP 2009
Monday, December 20, 2010
22
Magnetic
North
Distance
(km)
Magnetic
North Distance
(km)
2D Imaging of Convective Flows
400
350
300
250
200
150
100
50
!150
!100
!50
0
50
100
Magnetic East Distance (km)
150
Magnetic East Distance (km)
Monday, December 20, 2010
23
Dynamic 2D flow fields and auroral
forms
Courtesy Emma Spanswick and Eric Donovan
Monday, December 20, 2010
24
Dynamic 2D flow fields and auroral
forms
BUTLER ET AL.: ISR IMAGING OF F-REGION DRIFTS
Semeter
et al.
(JGRA
Butler
et
al. (RS
2010,
in press)
ER
ET AL.:
ISR
IMAGING
OF F-REGION
DRIFTS
ET
L.:
AL.:
ISR
IMAGING
ISR
IMAGING
OF 2010),
F-REGION
OF F-REGION
DRIFTS
DRIFTS
35
Plasma flow field
confirms optical
signature of
Harang reversal
BUTLER ET AL.: ISR IMAGING OF F-REGION DRIFTS
Figure 12. Another example similar to Figure 11.
35
Rapid (~30-sec)
coherent variations
in flow also
observed along
“quiet” arc
Similar dynamic observed by Bristow et al. (JGRA 2008) with SuperDARN
Monday, December 20, 2010
25
3D Imaging of the Ionospheric State
11x11 grid of beams
3 deg separation
Two pulse patterns:
13 Baud Barker code
480us uncoded pulse
14.6 s integration = 48 pulses/beam
Monday, December 20, 2010
26
Monday, December 20, 2010
27
83 (15.0° az, 89.0° el)
240
12
12
240
11.8
11.6
200
200
11.4
180
Log10 Ne
Altitude
(km)
Altitude (km)
220
11.2
11
160
11
160
10.8
140
10.6
120
120
10.4
100
09:00
9:00
Monday, December 20, 2010
10.2
09:05
09:10
9:10
09:15
09:20
9:20
09:25
UT
09:30
9:30
09:35
09:40
9:40
09:45
09:50
9:50
10
10
28
Rapid abatement of proton
precipitation preceding onset
83 (15.0° az, 89.0° el)
240
12
12
240
11.8
Altitude
(km)
Altitude (km)
220
11.6
200
200
11.4
180
11.2
11
160
11
160
10.8
140
10.6
120
120
10.4
100
09:00
9:00
Monday, December 20, 2010
10.2
09:05
09:10
9:10
09:15
09:20
9:20
09:25
UT
09:30
9:30
09:35
09:40
9:40
09:45
09:50
9:50
10
10
29
150
Altitude (km)
Integrated in x-y plane,
proton layer dynamics
become as clear as the
electron aurora.
80
83 (15.0° az, 89.0° el)
240
12
12
240
11.8
Altitude
(km)
Altitude (km)
220
11.6
200
200
11.4
180
11.2
11
160
11
160
10.8
140
10.6
120
120
10.4
100
09:00
9:00
Monday, December 20, 2010
10.2
09:05
09:10
9:10
09:15
09:20
9:20
09:25
UT
09:30
9:30
09:35
09:40
9:40
09:45
09:50
9:50
10
10
30
Non-thermal backscatter
Michell et al., Ann. Geophys. 2008, 2009;
Monday, December 20, 2010
31
Low altitude ionospheric turbulence
Oxygen 630 nm, ~1eV
50 km
Prompt emission
11 km
Semeter et al., GRL 2006, JGRA 2009
Monday, December 20, 2010
32
Non-thermal plasma
2007-03-23
1
_
EL=77.5
3
2
500 _
SNR (dB)
Altitude (km)
700
AZ=-154.3
300 _
100 _
|
|
0
10
1
|
|
|
20
30
40
seconds after 11:20:00 UT
2
|
|
50
60
3
Stromme et al., AGU Fall Meeting, 2007
Monday, December 20, 2010
33
Beam driven instability
Ions
Electrons
Electric
Field
Diaz et al., RS 2008, 2010
Monday, December 20, 2010
34
Beam destabilized plasma
96
Thermal
Langmuir (“Plasma Line”)
0
-3000
Ion-acoustic (“Ion Line”)
20
40
60
k = 2π λ
(a)
80
100
(1/m)
Beam Destabilized
3000
120
Frequency (kHz)
3000
Frequency (kHz)
96
0
-3000
20
40
60
k = 2π λ
(a)
80
100
(1/m)
120
Parametric decay of Langmuir waves produces enhancement in
ion-acoustic waves
Diaz et al., RS 2010
Monday, December 20, 2010
35
Summary
✤
What can be measured?
✤
✤
✤
3D imagery of evolving ionospheric state (Ne, Te, Ti, Vi)
Detailed studies of non-thermal plasma processes and their
causes.
What is yet to be done?
✤
Optimize radar modes for MIC research
✤
Conjugate studies satellites and rockets (incomplete)
✤
Assimilation with ancillary diagnostics
Monday, December 20, 2010
36